Question

1)Cho hình bình hành ABCD tâm o.Chứng minh:

a)AB-BC=DB

b)DA-DB+DC=VECTO KHÔNG

c)DA-DB=OD-OC

d) CO-OB=BA

e) MA+MC=MB+MD

f) MA+MB+MC+MD=4MD

g) BA+BC+OB=OD

h) AB+OD+OC=AC

2)Cho ngũ giác ABCDE.Chứng minh:

a) AB+BC+CD=AE-DE

b)AB+BC+CD+DA=VECTO KHÔNG

c) DA-CA=DB-CB

d)AC+DA+BD=AD-CD+BA

Answer 1

https://i.imgur.com/PCU6zZ4.jpg

Answer 2

Mk giải giùm 3 câu nhé chả dài quá :>>

Answer 3

2)

a)\(\overrightarrow{AB}+\overrightarrow{BC}+\overrightarrow{CD}=\overrightarrow{AE}-\overrightarrow{DE}\Leftrightarrow\overrightarrow{AD}=\overrightarrow{AE}+\overrightarrow{ED}\Leftrightarrow\overrightarrow{AD}=\overrightarrow{AD}\)

b)

\(\overrightarrow{AB}+\overrightarrow{BC}+\overrightarrow{CD}+\overrightarrow{DA}=\overrightarrow{0}\Leftrightarrow\overrightarrow{AA}=\overrightarrow{0}\)

c)

\(\overrightarrow{DA}-\overrightarrow{CA}=\overrightarrow{DB}-\overrightarrow{CB}\Leftrightarrow\overrightarrow{DA}+\overrightarrow{AC}=\overrightarrow{DB}+\overrightarrow{BC}\Leftrightarrow\overrightarrow{DC}=\overrightarrow{DC}\)

d)\(\overrightarrow{AC}+\overrightarrow{DA}+\overrightarrow{BD}=\overrightarrow{AD}-\overrightarrow{CD}+\overrightarrow{BA}\Leftrightarrow\overrightarrow{AC}+\overrightarrow{CD}+\overrightarrow{DA}-\overrightarrow{BA}+\overrightarrow{BD}-\overrightarrow{AD}=\overrightarrow{0}\Leftrightarrow\overrightarrow{AC}+\overrightarrow{CD}+\overrightarrow{DA}+\overrightarrow{AB}+\overrightarrow{BD}+\overrightarrow{DA}=\overrightarrow{0}\Leftrightarrow\overrightarrow{AA}=\overrightarrow{0}\)